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Aluminum joint problem

03-05-2008, 03:51 PM

I am trying to tig a t joint. Material is alum... .060 wall...1.5" x 3/8" extruded
box. Tig is Syncro 200. My problem is I can't seem to get my heat at the joint corner/seam. The filler will stick to either side of the joint and after enough
heat is applied, the filler can bridge the gap between the two making for a larger fillet than necessary. If I really apply heat directly at the joint,it may start to fall apart before I get the filler to flow. So far I suck at this.
Any suggestions? Tricks?

I'm far from an expert, but I was recently playing with aluminum T-joints as well. What ended up working for me, since the leg would melt the fastest, was to focus the heat a bit more on the base and occasionally flick it up a bit to the leg. When adding the filler, aim the rod more towards the leg and let it work itself into the joint. And if that fails, ignore my advice.

Comment

When you start an arc on aluminum, it wants to jump from one piece to the other, and not focus.

The solution is to start very hot, melt the filler into the joint (even if it looks like it's only bridging the gap), and after that you'll be able to add filler in the normal way, as the arc won't jump any longer, because your two pieces are now one.

Some people try to start the arc directly on the filler, placed in the joint.

-James

Comment

focus your arc on the bottom piece, remember-heat rises, this will also heat your vertical piece, allow your work to get up to temperature, add a little rod, adjust your torch angle, and you're off to the races...

Comment

I find that starting slow and getting some heat in the part works for me, it also gives more time for cleaning. as you see a bright spot (melting) start to form on one or both, add some filler to the root and it will quickly melt in, once that first spot is in place it will flow from there. I have also found that learning fillets on slightly thicker material helps.

Comment

Some things are easier to show than type I would just tell you to turn up the HZ but you can't
Anyway there have been a few good suggestions but the truth is if you are adding filler without heating the root you ain't helping anything. What I do is start more towards the middle than you want the bead to be and bring up the heat slowly. Sometimes I am angling the torch enuff to touch the cup on both parts of the joint at this stage. Sorta rock the cup/torch a bit as you bring up the heat and work BACKHAND slowly watching the shiny part on both sides come ever so closer together. when the 2 pools get to the edges they will either jump together or a keyhole will open...THEN feed filler and work forhand as usual. Any time you add filler before the root is fluid you are just bridging a gap add making the bead fat.
HTH.
Oh yea...make sure you got the tunsten out aways and grinding a point on it while using lanthanated would help also...prolly 3/32

Comment

Thanks for all the replies. They all make sense to me. I'll just keep trying untill it's correct.
Info....red 3/32 tung..
Shield gas 20cfh
amps 100
med start
3/32 filler..4043 I think
With stuff this light, I think preheat is not needed unless I could direct a small flame where the two meet.
How close can a magnetic dial indicator base on a 5/8" 44" x 96" steel table
be to the weld area and not affect the arc?

Comment

for your tungsten don't sharped it as much, since the electricity works from the cross section of the electrode this will move the arc closer to the joint. I know that intuition would say to make it sharper but that will move the arc bell up the electrode. reference AWS welding handbook eigth edition page 82 figure 3.5

Comment

Why do you say lose the red? What do you recommend? The reason I am using red is so many have stated that's all they use and pure tung (green) doesn't hold up as well.
I switched to green last night and noticed that the ball on the end of the tungsten is about the size diameter of the tung or slightly larger and the ball stays shiney.
The red would develop a ball but much smaller and you can still see the grind
angle of the tungsten.

Comment

Why do you say lose the red? What do you recommend? The reason I am using red is so many have stated that's all they use and pure tung (green) doesn't hold up as well.
I switched to green last night and noticed that the ball on the end of the tungsten is about the size diameter of the tung or slightly larger and the ball stays shiney.
The red would develop a ball but much smaller and you can still see the grind
angle of the tungsten.

I guess if the red is all you have then use it...I'm not much of a green lover either...it just goes away too fast for me. I don't like red because it eventually erodes too bad and grinding happens too much for me.
I much prefer to use the lanthanated on everything nowadays. It holds up well both AC and DC and doesn't erode as bad as red on AC.
I also like the smaller filler for the thin stuff.